Articles

A Note On Cost And Productivity Aspects Of The Novel MEX-Based Technologies

The Additive Manufacturing (3-D printing) technologies offer unique opportunities to make advanced prototypes or parts impossible to produce by any other means. In such cases, the cost or productivity is not of primary concern. However, as AM moves from the prototyping level to regular production it also starts to compete with other existing net-shape technologies, primarily in terms of productivity and cost. This has been addressed in a recent article by Brouse and Conlon (1) and few others.

Material Extrusion (MEX) 3D-printing technology typically uses a continuous powder-loaded filament of a feedstock, adapted to be compatible with the FFF (FDM)-type of printers. In the new generation of MEX-based technologies, the filament is replaced by feedstock that can be printed bydirect nozzle extrusion (BMPD = Bound Material Powder Deposition). In addition to substantially higher powder loading of the feedstock the benefits achieved include lower cost of raw material and not at least, of equipment. In the recently developed line of printers by Metallic3D (2) the cost of a printer unit has turned out to be close to that of the standard injection moulder unit supplied by the company Goceram (3) for medium pressure PIM (Powder Injection Moulding). These printers also turned out to be able to use the Goceram MEDPIMOULD® technology to make printable feedstock, in addition to another, recently developed solvent-base feedstock technology that does not require any debinding step for the shaped parts.

PRODUCTION COST ESTIMATE

Prior to any customer investment consideration, our company is always expected to produce an estimate of the anticipated cost per piece for the intended products in order to see if the production by MIM/CIM at all can be profitable. This makes it of interest to use the company standard calculation matrix, designed for this purpose, to compare the cost per unit manufactured by these two different technologies – as they share some processing steps, before/after the shaping step. In particular, it can be useful to be able to identify the respective cost drivers in these two different production technologies.

Fig, 1. Calculation matrix to estimate the production cost per part The calculation matrix for an intended low-volume production (15000 pcs per year) of 3-D printed stainless steel parts is shown in Fig. 1., with the assumptions as given and clarified below.

Corresponding matrix is regularly used for customers intending to make MIM parts. The operational costs (maintenance, water, gas etc) in the table are not to be taken at face value, the respective numbers shown are based mainly on customer feedback, they can vary. But more important, they should always be taken into consideration in order to get as complete a picture as possible. As seen in the table, this investment is fully financed by a loan running for 5 years with a 10 % interest rate.

The usually anticipated main cost drivers are the cost of equipment, raw material and work force, In the 3rd column of the matrix these cost drivers are seen to be approximately 20, 7 and 45 %, respectively, of the total cost. Despite the relatively inexpensive printer unit, the equipment cost is pushed up by the need of a sintering furnace (in case the client already does not have this type of equipment for other production). The powder is not a big cost driver in the AM case due to the low total output volume per year. Somewhat unexpectedly, the personnel cost is the largest cost driver, but maybe not surprising, also due to the relatively low production output. This clearly indicates the need of some automatization.

Corresponding calculation can be made for a MIM production of parts of the same mass but ten times larger yearly output (150000 pcs). The investment cost turns out to be almost a factor of two higher, mainly due to the additional cost of a debinder furnace plus multi-cavity tooling. But interestingly, in spite of that, the equipment cost driver remains the same, 20 %, thanks to the larger annual output. On the other hand, this will push up the powder cost, to the level of being the main cost driver at 35 %. The work force will need to add one more worker but the total cost will still be substantially lower, at 30 % (compared to 45 % in the low-volume AM production). And due to the ten times higher yearly output the cost per part will end up at 1,3 Euro per piece (five time less than the AM production).

One way for AM (to compete with MIM) and to deal with these cost drivers is of course, if relevant, to increase the overall productivity of the system, without significantly altering the other cost parameters. This is a possibility with some MEX printers. They can be equipped with multiple nozzles, simultaneously printing the same part. In this manner, the production volume can quickly be multiplied – in analogy to using multi-cavity tooling in MIM.

What this type of calculation matrix does not include is any complementary after-processing, in particular modification of the surface condition. The surface finish will always be an issue, as long as a reasonably high production rate is targeted - it is basically about either fine/slow or structured/fast. Also the plastic-based FDM/FFF/MEX printers have this issue. There are nowadays suppliers of automatic machines, with big barrels inside, performing a surface-smoothing sand blasting operation on plastic printed parts. Maybe this type of finishing could be used also on metal or ceramic parts. It could require some processing modification - perhaps pre-sintering - surface finishing- final sintering.

Finally it may also be added that a more easy way is to look for applications where the surface finish is not an issue. Actually, many products don't need a glossy surface - it is just a consequence of the production technology (MIM or CNC) used. There are also instances where the structured surface can be an advantage, such as heating elements where the increased surface area leads to higher thermal output. There may be more cases like that.

REFERENCES

1. D. Brouse and M. Conlon: The need for speed, and how the right powder can reduce AM part production costs by 50%, Metal Additive Manufacturing | Spring 2021 Vol. 7 No. 1, p. 147

2. D. Defelici: Metallic3D introduces new bound metal paste Additive Manufacturing machine, AM Metal Magazine, February 11, 2020

3. R.Pompe and J.Brandt: Goceram's MEDPIMOULD technology offers cost-effective PIM production, Metal Powder Report, Vol 56, Issue 6, June 2001, Pages 14-17